Whilst on holiday, Tom and Kate discover "Greyghost", a mysterious ruined house. On a return visit they encounter a strange ghostly mist which appears to transport them back through time to the period when the house was intact and occupied, where they meet Rebecca, a beautiful young girl who is confined to a wheelchair. In a further visit they do battle with the vile and villainous Uncle Ronald and Aunt Clarissa who are trying to take over Greyghost and send Rebecca away. After a ghostly experience in a cellar the three children make a desperate attempt to escape the clutches of the two villains and following a thrilling climax the mystery of Greyghost's past is finally revealed.